U.S. patent number 6,731,060 [Application Number 09/513,136] was granted by the patent office on 2004-05-04 for electron-emitting device, electron source using the electron-emitting device, and image-forming apparatus using the electron source.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Tamaki Kobayashi, Satoshi Mogi, Keisuke Yamamoto.
United States Patent |
6,731,060 |
Yamamoto , et al. |
May 4, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Electron-emitting device, electron source using the
electron-emitting device, and image-forming apparatus using the
electron source
Abstract
Disclosed is an electron-emitting device constructed by a pair
of electroconductors which are disposed so as to be opposite to
each other on a substrate and a pair of deposited films which are
arranged so as to be connected to the pair of electroconductors,
which are disposed so as to sandwich a gap, and which contain
carbon as a main component. In each of the deposited films,
phosphorus is contained in a range of 5 mol percent to 15 mol
percent with respect to carbon.
Inventors: |
Yamamoto; Keisuke (Yamato,
JP), Kobayashi; Tamaki (Isehara, JP), Mogi;
Satoshi (Kawasaki, JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
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Family
ID: |
26392636 |
Appl.
No.: |
09/513,136 |
Filed: |
February 25, 2000 |
Foreign Application Priority Data
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Feb 26, 1999 [JP] |
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11-052028 |
Feb 15, 2000 [JP] |
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2000-041451 |
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Current U.S.
Class: |
313/495; 313/310;
313/336 |
Current CPC
Class: |
H01J
1/316 (20130101) |
Current International
Class: |
H01J
1/316 (20060101); H01J 1/30 (20060101); H01J
001/62 () |
Field of
Search: |
;313/495,496,497,320,336,351,238,292,243,240,250,609,610,621 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 660 357 |
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Jun 1995 |
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EP |
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7-235255 |
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Sep 1995 |
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JP |
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2854385 |
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Nov 1998 |
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JP |
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Other References
H Araki, "Electroforming and Electron Emission of Carbon Thin
Films", Journal of the Vacuum, Society of Japan, 1983, pp. 22-29
(with English Abstract on p. 22). .
M. Hartwell, "Strong Electron Emisson from Patterned Tin-Indium
Oxide Thin Films", IEDM, 1975, pp. 519-521..
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Primary Examiner: O'Shea; Sandra
Assistant Examiner: Truong; Bao Q.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. An electron-emitting device comprising a pair of
electroconductors disposed on a substrate so as to be opposite to
each other and a pair of deposited films which are arranged so as
to be connected to said pair of electroconductors, and which are
disposed so as to sandwich a gap, and which contain carbon as a
main component, wherein in said deposited film, phosphorus is
contained within a range of 5 mol percent to 15 mol percent with
respect to carbon.
2. An electron-emitting device comprising a pair of device
electrodes arranged so as to be opposite to each other on a
substrate, an electroconductive film which is arranged so as to be
connected to said pair of device electrodes and which has a fissure
between the pair of device electrodes, and a deposit which is
formed in said fissure and a region including the fissure and which
has a gap with a width that is narrower than the fissure in the
fissure, wherein in said deposit, phosphorus is contained within a
range of 5 mol percent to 15 mol percent with respect to
carbon.
3. An electron source comprising a plurality of electron-emitting
devices according to claim 1 or 2 on a substrate and wirings
connected to said electron-emitting devices.
4. An image-forming apparatus comprising an electron source
according to claim 3 and an image-forming member for forming images
due to collision of electrons emitted from said electron
source.
5. An electron-emitting device comprising: a carbon film composed
chiefly of carbon; and an electrode electrically connected to the
carbon film, wherein phosphorus is contained in the carbon film in
a ratio of 15 mol% or less with respect to carbon.
6. An electron-emitting device comprising: a carbon film composed
chiefly of carbon; and an electrode electrically connected to the
carbon film, wherein phosphorus is contained in the carbon film in
a ratio of from 5 mol% to 15 mol% with respect to carbon.
7. An electron-emitting device comprising: a pair of
electroconductors disposed on a substrate; and a pair of films
connected to the pair of electroconductors, respectively, disposed
with a gap therebetween and containing carbon as a main component,
wherein phosphorus is contained in said films in a ratio of 15 mol%
or less with respect to carbon.
8. An electron-emitting device comprising: a pair of device
electrodes disposed on a substrate; electroconductive films
connected to the pair of device electrodes and having a first gap
between the pair of device electrodes; and a carbon film disposed
in the first gap and on the electroconductive films, having a
second gap narrower in width than that of the first gap, within the
first gap, and containing carbon as a main component, wherein
phosphorus is contained in the carbon film in a ratio of 15 mol% or
less with respect to carbon.
9. An electron-emitting device comprising: a pair of device
electrodes disposed on a substrate so as to face each other;
electroconductive films connected to the pair of device electrodes
and having a first gap between the pair of device electrodes; and a
carbon film disposed in the first gap on the electroconductive
films, having a second gap narrower in width than that of the first
gap, within the first gap, and containing carbon as a main
component, wherein phosphorus is contained in the carbon film in a
ratio of from 5 mol% to 15 mol% with respect to carbon.
10. An electron source comprising a plurality of electron-emitting
devices disposed on a substrate, and wirings connected to said
electron-emitting devices, wherein each electron-emitting device is
an electron-emitting device according to any one of claims 5 to
9.
11. An image-forming apparatus comprising an electron source
according to claim 10, an image forming member.
12. An electron-emitting device comprising: a carbon film composed
chiefly of carbon; and an electrode electrically connected to the
carbon film, wherein phosphorus is contained in the carbon film in
a ratio of 5 mol% or more with respect to carbon.
13. An electron source comprising a plurality of electron-emitting
devices disposed on a substrate, and wiring connected to said
electron-emitting devices, wherein each electron-emitting device is
an electron-emitting device according to claim 12.
14. An image-forming apparatus comprising an electron source
according to claim 13, and a phosphor arranged to emit light in
response to being irradiated with an electron emitted from said
electron source.
15. An electron-emitting device comprising: a deposit composed
chiefly of carbon including a graphite structure; and an electrode
electrically connected to the deposite, wherein phosphorus is
contained in the deposit.
16. An electron source comprising a plurality of electron-emitting
devices disposed on a substrate, and wirings connected to said
electron-emitting devices, wherein each electron-emitting device is
an electron-emitting device according to claim 15.
17. An image-forming apparatus comprising an electron source
according to claim 16, and a phosphor arranged to emit light in
response to being irradiated with an electron emitted from said
electron source.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron-emitting device, an
electron source comprising it, and an image-forming apparatus such
as a display as its application. More particularly, the invention
relates to a surface conduction electron-emitting device with a
novel construction, an electron source using it, and an
image-forming apparatus such as a display as its application.
2. Related Background Art
A surface conduction electron-emitting device utilizes a phenomenon
that electrons are emitted by allowing an electric current to flow
into an electroconductive film formed on a substrate.
As an example of the surface conduction electron-emitting device,
the use of an SnO.sub.2 thin film for a device of this type [M. I.
Elinson, "Radio Eng. Electron Phys.", 10, 1290, (1965)], the use of
an Au thin film [G. Ditmmer, "Thin Solid Films", 9, 317 (1972)],
the use of an In.sub.2 O.sub.3 /SnO.sub.2 thin film [M. Hartwell
and C. G. Fonsted, "IEEE Trans. ED Conf.", 519 (1975)], the used of
a carbon thin film [Hisashi Araki et al., "Shinku (Vacuum)", Vol.
26, No. 1, p. 22 (1983)], and the like have been reported.
In the above surface conduction electron-emitting device, prior to
emitting electrons, the electroconductive film is generally
subjected to an energization operation called "forming", thereby
obtaining a state where the electron emission is caused.
In this instance, "forming" is such an operation that a constant
voltage or a voltage which gradually rises at a rate of, for
example, about 1 V/min. is applied across the electroconductive
film to allow a current to flow into the electroconductive film,
and the electroconductive film is partially broken, deformed, or
modified to enter an electrically high-resistant state, thereby
obtaining a state where electrons are emitted.
Owing to the operation, a fissure is formed in a part of the
electroconductive film. The phenomenon of the electron emission is
attributed to the presence of the fissure. Although it is not
completely clarified which portion the electron emission actually
occurs in the fissure and a region around it are called "electron
emitting portion" for convenience in some cases.
The present applicant has already expressed many proposals
regarding the surface conduction electron-emitting device. For
instance, the applicant has disclosed that it is preferable to
perform the above "forming" by applying a pulse voltage to the
electroconductive film in Japanese Patent No. 2854385 and U.S. Pat.
Nos. 5,470,265 and 5,578,897.
In this instance, a waveform of the pulse voltage can be obtained
by either one of a method of holding a peak value constant as shown
in FIG. 5A and a method of gradually raising a peak value as shown
in FIG. 5B. In consideration of the form and material of the device
and forming conditions, it can be suitably selected.
It is found that subsequent to the forming, the pulse voltage is
repetitively applied to the electron-emitting device in an
atmosphere containing an organic material, so that both of a
current (device current If) flowing into the device and a current
(emission current Ie) accompanying with the electron emission
increase. Such an operation is called "activation".
The operation forms a deposit containing carbon as a main component
in the region including the fissure formed by the "forming" in the
electroconductive film. The details of the operation are disclosed
in Japanese Patent Application Laid-Open No. 7-235255.
When the above surface conduction electron-emitting device as
mentioned above is applied to an image-forming apparatus, it is
further required that the device has a low electric consumption and
high luminance.
As properties of the electron-emitting device, therefore, it is
required to further raise a ratio of the emission current Ie to the
device current If, namely, an electron-emitting efficiency more
than ever.
It is a matter of course that when such properties are improved, it
is necessary that an aging change in properties by continuing the
electron emission is not larger than that of the conventional
technique.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an
electron-emitting device excellent in electron-emitting
characteristics, an electron source using it, and an image-forming
apparatus using it.
According to the present invention, there is provided an
electron-emitting device comprising a pair of electroconductors
disposed on a substrate so as to be opposite to each other; and a
pair of deposited films which are arranged so as to be connected to
the pair of electroconductors, respectively, and which are disposed
so as to sandwich a gap, and which contain carbon as a main
component, wherein in the deposited film, phosphorus is contained
within a range of 5 mol percent to 15 mol percent with respect to
carbon.
According to the present invention, there is provided an
electron-emitting device comprising a pair of device electrodes
arranged so as to be opposite to each other on a substrate, an
electroconductive film which is arranged so as to be connected to
the pair of device electrodes and which has a fissure between the
pair of device electrodes, and a deposit which is formed in the
fissure and a region including the fissure, which has a gap with a
width that is narrower than the fissure in the fissure, and which
contains carbon as a main component, wherein in the deposit,
phosphorus is contained within a range of 5 mol percent to 15 mol
percent with respect to carbon.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are schematic views showing a schematic
construction of an electron-emitting device according to a
practical mode of the present invention:
FIG. 2 is a schematic cross-sectional view of the electron-emitting
device according to the practical mode of the present
invention;
FIGS. 3A, 3B, 3C and 3D are views for explaining a manufacturing
process of the electron-emitting device according to an embodiment
of the present invention;
FIG. 4 is a block diagram showing the outline of an evaluating
apparatus for the electron-emitting device according to the
embodiment of the present invention;
FIGS. 5A and 5B are pulse voltage waveform chart which is used in a
forming process when the electron-emitting device according to the
embodiment of the present invention is formed;
FIG. 6 is a schematic diagram of an electron source according to
the embodiment of the present invention;
FIG. 7 is a schematic partially cutaway cross-sectional view in
perspective of an image-forming apparatus utilizing the electron
source shown in FIG. 6;
FIG. 8 is a schematic diagram showing another construction of the
electron source according to the embodiment of the present
invention;
FIG. 9 is a schematic partially cutaway cross-sectional view in
perspective of an image-forming apparatus utilizing the electron
source shown in FIG. 8; and
FIG. 10 is a pulse voltage waveform chart which is used in an
activation process when the electron-emitting device according to
the embodiment of the present invention is formed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to the present invention, in an electron-emitting device
comprising a pair of electroconductors which are arranged so as to
be opposite to each other on a substrate; and a pair of deposited
films which are arranged so as to be connected to the pair of
electroconductors, respectively, which are disposed so as to
sandwich a gap, and which contain carbon as a main component, each
of the deposit films contains phosphorus within a range of 5 mol
percent to 15 mol percent with respect to carbon.
According to the present invention, in an electron-emitting device
comprising: a pair of device electrodes arranged so as to be
opposite to each other on a substrate; an electroconductive film
which is arranged so as to be connected to the pair of device
electrodes and which has a fissure between the pair of the device
electrodes; and a deposit which is formed in the fissure and a
region including the fissure, which has a gap having a width that
is narrower than the fissure in the fissure, and which contains
carbon as a main component, the deposit contains phosphorus within
a range of 5 mol percent to 15 mol percent with respect to
carbon.
According to the present invention, there is provided an electron
source comprising a plurality of the above electron-emitting
devices arranged on a substrate and wirings which are connected to
the electron-emitting devices.
According to the present invention, there is provided an
image-forming apparatus comprising the above electron source and an
image-forming member for forming images due to collision of
electrons emitted from the electron source.
Preferred practical modes of the present invention will now be
illustratively described in detail by referring to the drawings.
The dimension, material, form, relative arrangement, and the like
of each of constitutional members which will be described in the
practical modes never intend to limit the scope of the invention
unless otherwise specified.
Referring to FIGS. 1A and 1B, a fundamental construction of an
electron-emitting device according to a practical mode of the
present invention will now be described. FIGS. 1A and 1B are
schematic views illustrating a schematic construction of the
electron-emitting device according to the practical mode of the
present invention. FIG. 1A is a schematic plan view. FIG. 1B is a
sectional schematic view (cross-sectional view taken along the line
1B--1B in FIG. 1A).
In FIGS. 1A and 1B, on a substrate 1 as a base made of an
insulating material, a pair of device electrodes 2 and 3 arranged
so as to be opposite to each other are provided. An
electroconductive film 4 arranged so as to be connected to the pair
of device electrodes 2 and 3 is formed.
The illustration shows a case where an electroconductors is
constructed by the device electrodes 2 and 3 and the
electroconductive film 4 as mentioned above. Even when the
electroconductive film 4 is eliminated and the electroconductor is
constituted by the device electrodes 2 and 3 only, the
electroconductor can exhibit the similar function as an
electron-emitting device.
Referring to FIGS. 1A and 1B, reference numeral 5 schematically
denotes a fissure formed in the electroconductive film 4. The
fissure 5 is formed between the pair of device electrodes 2 and
3.
Referring to FIGS. 1A and 1B, a deposit (deposited film) 10
contains carbon as a main component. In this case, the deposit 10
in the illustration is formed on the electroconductive film 4
alone. Depending on a forming method, it is also formed on the
device electrodes 2 and 3. It is also formed on the substrate 1
except for the inside region of the fissure 5 in some cases.
The deposit 10 containing carbon as a main component is formed not
only around the fissure 5 but also in the fissure 5. The deposit 10
is formed in the fissure 5 so as to have a gap that is narrower
than the fissure 5.
As another fundamental construction of the electron-emitting
device, there is a step type device shown in FIG. 2. FIG. 2 is a
schematic cross-sectional view of the electron-emitting device
according to the practical mode of the present invention.
Referring to FIG. 2, a step-forming member 21 made of an insulating
material is formed on the substrate 1 in order to form a step.
Except for the member 21, the fundamental construction is the same
as that shown in FIGS. 1A and 1B and the component elements are
designated by the same reference numerals.
As required properties of the device electrodes 2 and 3, it is
necessary to have enough electroconductive properties. As a
material, metal, alloy, or electroconductive metallic oxide, or a
printed conductor or semiconductor made from a mixture of the above
material and glass or the like are mentioned.
In order to preferably form a fissure due to the forming, namely,
preferably impart electron-emitting ability, it is preferable to
form the electroconductive film 4 by using fine particles made of
an electroconductive material. As a material, for example, an
electroconductive material such as Nj, Au, PdO, Pd, or Pt can be
used.
Among them, PdO is preferably used because of the following
advantages. After an organic Pd composition film is formed, it is
baked in an atmosphere, so that an electroconductive film
comprising fine particles can be easily formed. Since the film is a
semiconductor, it has an electric conductivity that is relatively
lower than that of metal, it can be easily controlled so as to
obtain a proper resistance value for the forming, and it can be
relatively easily reduced. Consequently, after the fissure is
formed due to the forming operation, the film is brought into
metallic Pd, so that the resistance can be reduced.
The deposit 10 containing carbon as a main component can be formed
by the above-mentioned "activation" method.
For controlling a content of phosphorus (hereinbelow, referred to
as P) contained in the deposit 10 containing carbon as a main
component, there can be used a method of introducing a raw gas
containing P to an atmosphere containing an organic material during
activation to control its amount, or a method of forming a deposit,
applying a solvent containing P in a form of an organic metallic
composition or the like to the deposit, performing a heat treatment
to allow the deposit to contain P, and to thereby control the
amount of the applied solvent.
According to the examination by the present inventor et al., it was
clarified that when P of 5 mol percent or more was contained with
respect to carbon, such an effect that an electron-emitting
efficiency raised was found.
On the other hand, it turned out that when the content was too
much, in the case where the electron-emission was successively
performed, a decreasing speed of the emission current became faster
than that in the case where P was not contained (namely, the
stability is deteriorated). As for the problem, the present
inventor et al. also found that when the content of P was 15 mol
percent or less with respect to carbon, a serious influence was not
actually exerted to the stability, so that the present invention
was accomplished.
Although the reason is not sufficiently seized, it is found that at
least part of the deposit containing carbon as a main component has
a graphite structure. It is well known that when P is contained in
graphite, the electroconductive properties are improved. The
present inventors infer that such a fact advantageously operates
upon improvement of the electron-emitting efficiency. For the
reason why an increase in content causes a serious influence on
stability, the present inventors infer that it is concerned with a
decrease in crystallinity of the portion with the graphite
structure.
Subsequently, a more specific embodiment constructed on the basis
of the practical mode of the present invention will now be
described.
(Embodiment of Electron-emitting Device)
An electron-emitting device according to the present embodiment has
the same construction as that shown in FIGS. 1A and 1B.
A method of manufacturing the electron-emitting device according to
the present embodiment will now be explained with respect to FIGS.
1A and 1B and 3A to 3D.
(Process-a)
First, on a cleaned quartz substrate 1, a photoresist pattern is
formed so as to have openings corresponding to the forms of the
device electrodes 2 and 3. By a vacuum evaporation method, Ti is
deposited at a thickness of 5 nm and Pt is subsequently deposited
at a thickness of 30 nm on it.
The photoresist pattern is resolved and eliminated by an organic
solvent. By a lift-off method, electrodes made of a Pt/Ti deposited
film are formed. In this instance, an electrode interval L is set
to 50 .mu.m and an electrode width W is set to 300 .mu.m (FIG.
3A).
(Process-b)
A Cr film is formed at a thickness of 100 nm by the vacuum
evaporation method. The Cr film is patterned so as to have an
opening corresponding to the form of an electroconductive film,
which will be described hereinlater, by a photolithography method.
After that, a solvent of an organic Pd composition (ccp4230
manufactured by Okuno Pharmaceutical Industries Co., Ltd.) is
applied to the resultant film by using a spinner. After the film
coated with the solvent is dried, it is subjected to a heat
treatment at a temperature of 350.degree. C. in an atmosphere for
12 minutes.
An electroconductive film comprising PdO fine particles with a
thickness of 10 nm by the above process. A sheet resistance Rs of
the film is equal to 2.times.10.sup.4 .OMEGA./.quadrature..
When it is assumed that when a resistance value measured by
supplying a current to the film having a length l and a width w in
the longitudinal direction is set to R, the sheet resistance Rs is
expressed by the following equation.
In the case where the film is uniform, when it is assumed that a
resistivity is set to .rho. and a film thickness is set to t, the
sheet resistance Rs is expressed by the following equation.
(Process-c)
The Cr film is removed by a Cr etchant. The electroconductive film
is patterned into a desired form by the lift-off method (FIG.
3B).
(Process-d)
The device is set in a vacuum processing apparatus. A pressure in a
vacuum chamber is decreased to 2.7.times.10.sup.-4 Pa by an exhaust
apparatus. After that, a pulse voltage is applied to a portion
between the device electrodes 2 and 3 to perform the forming
operation, thereby forming the fissure 5 in a part of the
electroconductive film (FIG. 3C).
The waveform of the pulse voltage used for the forming operation is
shown in FIG. 5B. The process is performed under such conditions
that a pulse width T1 is equal to 1 msec., a pulse interval T2 is
equal to 10 msec, and a peak value is gradually increased at a rate
of 0.1V per step.
During the process, a rectangular pulse voltage having a peak value
of 0.1V is inserted between the above pulse voltages and current
values are measured, thereby obtaining the resistance value of the
device. When the resistance value obtained as mentioned above
exceeds 1 M.OMEGA., applying the pulse voltage is stopped and the
forming operation is finished.
(Process-e)
Subsequently, the activation operation is performed. Exhausting the
vacuum chamber is continued. After the pressure in the chamber is
dropped to 1.3.times.10.sup.31 6 Pa, a mixture of benzonitrille and
trimethylphosphoric acid is introduced to the chamber through a
slow leak valve attached to the vacuum chamber. The slow leak valve
is controlled so that the partial pressure of benzonitrille is
equal to 1.3.times.10.sup.-4 Pa. Controlling the ratio of
benzonitrille to trimethylphosphoric acid can control the content
of P contained in the deposit containing carbon as a main
component, which is formed in the activation operation.
The pulse voltage is applied to the portion between the device
electrodes 2 and 3. The waveform of the applied pulse voltage is a
rectangular pulse as shown in FIG. 10, whose polarity is inversed
every pulse. The pulse voltage is applied for 60 minutes under such
conditions that the pulse width T1 is equal to 1 msec., pulse
interval T2 is equal to 100 msec., and peak value of the pulse
voltage is set to 15V. (Pulse applying time is obtained as time
until increasing the device current If is saturated under such
processing conditions by a preliminary examination.)
In the region including the fissure 5 formed in the
electroconductive film by the process, the deposit 10 containing
carbon as a main component is formed. The deposit 10 containing
carbon as a main component is deposited in the fissure 5 so as to
form a gap 6 that is narrower than the fissure 5 (FIG. 3D).
In this manner, there were formed a sample containing P of 5 mol
percent in the ratio to carbon (embodiment 1), one containing P of
9 mol percent (embodiment 2), one containing P of 15 mol percent
(embodiment 3), and one containing P of 18 mol percent (comparative
example 2). Further, a sample to which P was not added (comparative
example 1) was also prepared for comparison.
Since a relation between the ratio of benzonitrile to
trimethylphosphoric acid and the content of P contained in the
deposit containing carbon as a main component varied depending on
the vacuum apparatus or conditions for the activation operation,
the relation was obtained by the preliminary examination and the
conditions at that time were applied. At that time, the content of
P was measured by a photoelectron spectroscopy method. An apparatus
used was ESCA LAB 220I-XL manufactured by VG Scientific Co.,
Ltd.
In the measurement, the ratio of P/C was obtained from the 2p peak
of P and the 1s peak of C (carbon) observed in a region in which
each side was equal to 50 .mu.m around the fissure as a center. The
measurement limit of P under such conditions was equal to about 0.1
mol percent.
(Process-f)
The vacuum chamber is exhausted and the vacuum chamber and device
are held at 250.degree. C. for 10 hours. The operation is performed
in order to eliminate water and molecules of the organic material
adsorbed to the device or inside of the vacuum chamber. The
operation is called a "stabilization operation".
As for the device, electron-emitting characteristics and its aging
change were measured by using the apparatus whose outline was shown
in FIG. 4.
Namely, a rectangular pulse voltage having a pulse width of 1
msec., a pulse interval of 100 msec., and a peak value of 15 V was
applied to the device by a pulse generator 41. A distance H between
the device and an anode electrode 44 was set to 4 mm. A constant
voltage of 1 kV was applied to the anode electrode 44 by a
high-voltage power source 43. At that time, the device current If
was measured by an ammeter 40 and the emission current Ie was
measured by an ammeter 42 to obtain an electron-emitting efficiency
.eta.=(Ie/If).
It was found that when the device was continuously driven, both of
Ie and If gradually decreased and, when the content of P was
increased to some degree, the decrease of Ie and If became faster
than that of a case where P was not contained. The comparison of
values of the electron-emitting efficiency at the beginning of the
measurement and the situation of the decrease of Ie and If are
shown in the following TABLE 1.
TABLE 1 Comparative Comparative example 1 Embodiment 1 Embodiment 2
Embodiment 3 example 2 P/C(mol %) 0 5.0 9.0 15.0 18.0 .eta. (%)
0.12 0.15 0.16 0.17 0.17 Aging change -- .smallcircle.
.smallcircle. .smallcircle. x
In TABLE 1, symbol .largecircle. denotes that the situation of the
decrease of Ie and If is not different from that of the sample
containing no P (comparative example 1) and symbol .times. denotes
that the decrease of Ie and If is faster than that of the
comparative example 1.
As a result, it turned out that when the deposit containing carbon
as a main component contained P of 5 to 15 mol percent, the
electron-emitting efficiency was raised and, as compared with the
case where such atoms were not contained, a change in Ie and If due
to the aging change was not increased, so that preferable results
were obtained.
(Embodiment of Electron Source and Image-forming Apparatus)
A plurality of electron-emitting devices according to the practical
modes or embodiments of the present invention are arranged on the
substrate and wirings which are connected to the devices are
formed, so that an electron source can be formed.
FIG. 6 shows a constructional example. In the diagram, reference
numeral 71 denotes a substrate; 72m X-directional wirings Dx1 to
Dxm; 73n T-directional wirings Dy1 to Dyn; 74 an electron-emitting
device according to the practical modes or embodiments of the
present invention; and 75 a connection for connecting the wiring
and the device. An insulating layer (not shown) is arranged on the
intersection of the X-directional wiring and the Y-directional
wiring so as to electrically insulate both of them from each
other.
An image-forming apparatus can be constituted by the above electron
source and an image-forming member for forming images by
irradiating electrons emitted from the electron source.
FIG. 7 shows a constructional example. In the diagram, an envelope
88 is constructed by a rear plate 81, a supporting frame 82, a
glass substrate 83, and a face plate 86. The above-mentioned
electron source is disposed in the envelope 88. The inside of the
envelope 88 can be sealed airtight.
External terminals Dox1 to Doxm and Doy1 to Doyn are connected to
the X-directional wirings Dx1 to Dxm and the Y-directional wirings
Dy1 to Dyn. Reference numeral 84 denotes an image-forming member 84
made from phosphor or the like. A metal back 85 made of a metallic
deposited film reflects light, which is emitted from the
image-forming member 84 to the inside of the envelope 88, to the
outside to improve a luminance and serves as an anode electrode for
accelerating electrons emitted from the electron source.
A high-voltage terminal 87 which is connected to the metal back 85
is connected to a power source for applying a high voltage to the
metal back (anode electrode) 85.
In the illustration shown in FIG. 7, the rear plate 81 is provided
separately from the substrate 71 for the electron source. When the
substrate 71 has enough strength, it can be also used as a rear
plate.
As a construction of the electron source, a construction shown in
FIG. 8 can be used. That is, a plurality of wirings 112 are formed
in parallel on a substrate 110. A plurality of electron-emitting
devices 111 are arranged between a pair of wirings to form a
plurality of device rows.
FIG. 9 shows a constructional example of the image-forming
apparatus utilizing the electron source with such a construction.
In case of such a construction, a plurality of grid electrodes 120
extending in the direction perpendicular to the direction of the
device rows of the electron source are arranged and have a function
to modulate an electron beam emitted from the electron-emitting
device belonging to one row selected from among the device rows by
a driving circuit.
Each grid electrode has an electron pass hole 121 to allow
electrons to pass at a position corresponding to the
electron-emitting device.
The external terminals Dox1 to Doxm are connected to the wirings.
FIG. 9 shows a case where the wiring of the even numbers and the
wirings of the odd numbers are led out from the side surface of the
supporting frame on the opposite side. Grid external terminals G1
to Gn are connected to the grid electrodes, respectively.
As described above, according to the present invention, phosphorus
is contained within a range of 5 mol percent to 15 mol percent with
respect to carbon in the deposited film containing carbon as a main
component, so that the electron-emitting efficiency can be improved
within a range where a serious influence is not exerted due to the
aging change by driving.
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